import java.util.Scanner;

public class GradeCal
{
	
public static void main(String[] args) 
{
		
 String grade;
		
int mark;
	Scanner sc=new Scanner(System.in);
		 
System.out.print(" Input mark :  ");
		
 
mark =sc.nextInt();
		  
if(mark>=100) grade="YOUR MARK OVER FLOW";
		
else if(mark>=80) grade="A";
		
else if(mark>=75) grade="B+";
else if(mark>=70) grade="B";
		
else if(mark>=65) grade="C+";
		
else if(mark>=60) grade="C";
		
else if(mark>=55) grade="D+";
		
else if(mark>=50) grade="D";
		
else if(mark<0) grade="YOUR MARK UNDER FLOW";
		
else grade="F";	
		
System.out.println("Mark = "+mark+"  Grade = "+grade);
		
}


